1. Field of the Invention
This invention relates to a method and apparatus for recording picture information onto recording material in the form of single sheets. More specifically, the invention produces photographic copies using a medium-capacity photographic singlesheet printer, of the kind typically employed in combined copier and developer equipment (e.g., minilabs).
2. State of the Art
In typical single-sheet printers, sheets of copy material of a desired size are fed sequentially into an exposure station of a printer. The sheets are exposed to light to form a picture in a pixel-by-pixel fashion. Exposure is performed, for example, by a cathode ray tube or a laser exposure device and delivered to a paper processor downstream of the printer. The exposure station of the printer is normally adapted to the largest size of copy material sheets (e.g., approximately 300 mm.times.450 mm). Experience teaches, however, that the larger sizes are not needed as often as the standard sized sheets (e.g., 100 mm.times.150 mm). This means that the printer operates at a far lower throughput than it is designed for. Throughput is the total surface area of all the sheets of copy material exposed per reference unit of time. For example, a typical minilab with a line exposure unit and an exposure width of 300 mm, which is required for the large picture sizes of 300 mm.times.450 mm, attains a linear speed of about 25 mm per second. If standard-sized prints (100 mm x 150 mm) are exposed longitudinally, then one print takes six seconds, which is equivalent to an output of 600 prints per hour. This comparatively low output resulting from the large exposure width is not economical for such a relatively expensive device. Normally, a printer should be able to output 1800 or more prints per hour.
In a printer with a line exposure unit, the throughput for smaller sizes could, theoretically, be increased by increasing the scanning speed and at the same time adapting the paper speed. But this could be done only in discrete steps, and would necessitate mechanical reverses at the polygonal mirror, would require substantially greater precision, and would not allow for fast changes. Hence, there is no thought of employing this arrangement in actual practice.
The problem discussed above in terms of a single-sheet printer, such as a minilab, logically exists in other recording apparatuses as well, such as printers of most of the various technologies that are designed for sheet-like recording material of varying sizes and that cannot attain their full output at relatively small sheet sizes.